Fluid-operated balancing hoist

ABSTRACT

A pneumatic balancing hoist comprising a frame rotatably supporting a hollow drum upon which is wound a cable or similar flexible element. The hollow drum includes a pressure chamber containing a piston movable in response to pressurization of the chamber. The piston includes a plurality of cam rollers which are each engaged with a rotatable cam member. The cam members are also formed as planet gears of a planetary gear drive in which a planet gear carrier is formed as an end wall of the hollow drum. The planet gears are engaged with a stationary sun gear fixed to the frame. In response to valving compressed air to the pressure chamber the piston and cam rollers force the cam members to rotate whereby the drum is operated to wind the cable thereon to raise and balance a load.

Uiied tent 3,556,485 l/l97l Orr 3,367,633 2/1968 Kratzeretal.

ABSTRACT: A pneumatic balancing hoist comprising a frame rotatably supporting a hollow drum upon which is Wound a cable or similar flexible element. The hollow drum includes a pressure chamber containing a piston movable in response to pressurization of the chamber. The piston includes a plurality of cam rollers which are each engaged with a rotatable cam member. The cam members are also formed as planet gears of a planetary gear drive in which a planet gear carrier is formed as an end wall of the hollow drum. The planet gears are engaged with a stationary sun gear fixed to the frame. in response to valving compressed air to the pressure chamber the piston and cam rollers force the cam members to rotate whereby the drum is operated to wind the cable thereon to raise and balance a load.

FLUID-OPERATED BALANCING HOIST BACKGROUND OF THE INVENTION Balancing hoist or load balancers have many applications in industry wherein it is desired to manually move heavy tools or workpieces with a minimum of effort. Known types of balancing hoists are generally characterized by a rotatable drum for winding a cable thereon and suitably connected to a pressure fluid actuator such as a cylinder and piston deviceQFluid in the actuator is maintained at a regulated pressure sufficient to offset or counterbalance the weight of the load permitting manual raising or lowering of the load with a force which is a mere fraction of the weight of the load. Examples of known types of balancing hoists are disclosed in US. Pat. Nos. 2,939,431; 3,260,508; and 3,286,989.

Generally it is desirable to provide a balancing hoist having mechanism which is simple in construction and which has negligible friction thereby minimizing the manual efiort necessary to raise and lower the load. Many prior art balancing hoists are unduly complicated which not only reduces their reliability but they accordingly require substantial manual effort to overcome the friction of their moving parts when moving the load. Moreover, efforts to provide a'hoist having a cable drum which translates as it rotates to maintain the cable in a fixed position have resulted in complicated mechanisms which offer no particular advantage for the relatively short hoisting distances of most balancing hoist applications.

SUMMARY OF THE INVENTION The present invention provides for a fluid-operated balancing hoist having an improved mechanism operable to convert the reciprocating motion of a piston located in a pressure fluid chamber into rotary motion fbr rotating a hoist drum. The present invention is characterized by a balancing hoist having a rotatable cable drum containing the hoist mechanism substantially within the drum itself thereby providing a compact and mechanically reliable device.

The present invention advantageously provides for a fluidoperated balancing hoist which is further characterized in that substantially all mechanical motion is of the rolling contact type whereby frictional forces resisting manual positioning of a balanced load are minimized. A further advantage of the present invention resides in the provision of a balancing hoist having a rotatable cable drum which is supported on rolling contact bearings located adjacent each end of the drum thereby eliminating any overhanging loads on the drum itself and also eliminating the need for an axially movable drum to keep the load in a fixed position with respect to the drum supports. These advantages as well as other objectives which have been realized with the balancing hoist of the present invention may be appreciated upon reading the disclosure set forth herein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of the balancing hoist of the present invention.

FIG. 2 is a longitudinal section of the balancing hoist illustrated in FIG. 1 and is taken along the line 2--2 ofFIG. 3.

FIG. 3 is a transverse section taken along the line 33 of FIG. 2.

FIG. 4 is a view of one ofthe cam gear members.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 a pressure fluid operated balancing hoist in accordance with the present invention is illustrated and generally designated by the numeral 10. The balancing hoist includes a frame 12 adapted to be hung by means of integral lugs 13 from a movable hoist trolley 14. The trolley 14 is movable along the I-beam section overhead rail 16 and is retained thereon by the flanged wheels 18. The balancing hoist 10 includes a cylindrical cable drum 20 rotatably mounted on the frame 12 and provided with a helical groove 22 adapted to wind a length of flexible cable 24 or the like thereon in response to rotation of the drum. As shown in FIG. I, the cable 24 has a hook 26 attached to its free end and a load such as the crankshaft 28 suspended from the hook. The load is merely representative of a variety of objects such as tools, workpieces, etc., normally associated with the use of a balancing hoist.

The balancing hoist 10 is designed to be operated with compressed air supplied from a source, not shown, by way of a conduit 30 leading to a suitable control system located within the enclosure 32 on the frame 12. One type of control system which will operate the balancing hoist 10 is disclosed in U.S. Pat. No. 2,939,431 to J. D. Bottje et al. A conduit 34 leads from the control system enclosure 32 to the interior of the drum 20 in a manner to be explained herein. The control system for the balancing hoist 10 further includes a depending flexible hoselike member 36 containing a plurality of fluid conduits and leading to a suitable control handle, not shown, whereby the balancing hoist may be operated to raise, lower, or balance the load 28.

Referring to FIGS. 2 and 3, the frame 12 includes an elongated shaft member 38 removably secured to the frame by means of a nut 40 threaded over one end of the shaft. The shaft 38 is nonrotatably retained with respect to the frame 12 by suitable means such as the key 42. As shown in FIG. 2, the cable drum 20 is rotatably supported on the stationary shaft 38 by means of rolling element bearings 44 and 46.

The cable drum 20 is formed by transverse end plates 48 and 50 suitably fastened to cylindrical portions 52 and 54, the latter including the helical groove 22 for receiving the cable 24 and an opening 51 for receiving a cable anchor 53. The construction of the cable drum 20 is such as to form a hollow interior 55 which is adapted to house drive means for rotatably driving the drum, said drive means being generally designated by the numeral 56. The drive means 56 includes a piston 58 axially movable with respect to the shaft 38 and sealingly engaged with the inner wall of the cylindrical portion 52 to form a pressure chamber 60. The piston 58 is axially movable with respect to the axis of rotation of the drum 20 which coincides with the longitudinal axis 37 of the shaft 38, and is rotatably supported in part on the shaft by means of the roller bearing 62. Annular seals 64, 66 and 68 prevent leakage of pressure fluid from the pressure chamber 60. Additional support of the piston is provided by the cylindrical portion 52 through the seal member 64. An annular resilient member 70 is attached to the face 72 of the piston 58 to prevent damaging impacting of the end plate 48.

The piston 58 includes a plurality of bifurcated pillars 74 extending into the hollow interior of the cable drum 20. The pillars 74, three in number, are each adapted to support a flanged roller 76 rotatably mounted by means of a shaft 78 journaled in roller bearings 79. The rollers 76 comprise means interconnecting the piston 58 and the drum 20 and operable in response to axial movement of the piston away from the end plate 48 to cause the drum to rotate and wind the cable 24 thereon. The interconnecting means further comprises a plurality of integral cam gear members 80 rotatably mounted on a stub shafts 82 by means of roller bearings 83. The members 80, also three in number, are identical in construction and are carried by the end plate 50. The members 80 are equally spaced around the shaft 38 and the gear portions 84 are each enmeshed with an integral gear portion 85 on said shaft. The members 80 also include integral portions 86, FIG. 4, forming circular cams having inclined surfaces 88 operable to be engaged with the rollers 76. The cam surfaces 88 are designed to have a uniform slope with respect to the rotational axes of the members 80 through approximately 300 of circular arc in a plane perpendicular with respect to said axes.

As may be appreciated from the drawings, movement of the piston 58 toward the members 80 will cause the rollers 76 to roll along the inclined surfaces 88 and act as cam drivers forcing the members 80 to rotate about the axis of their respective stub shafts 82. Due to the gear portion 85 on the shaft 38 being stationary with respect to the frame 12 the cam gear members 80 will also be forced to rotate about the longitu-v dinal axis 37 of the shaft 38 and accordingly cause rotation of the drum 20, in a manner similar to a planetary gear drive. By providing a suitable ratio of numbers of gear teeth between the cam gear members 80 and the fixed gear portion 85 a suitable number of revolutions of the drum 20 may be obtained for approximately a complete traversal of the rollers 76 along the cam surfaces 88.

Referring to FIG. 3, the arrangement of the cam driving rollers 76 with respect to cam gear members 80 is such that the lines of action of the reaction forces between the cam surfaces 88 and the rollers pass radially through the axis of the shaft 38 as indicated by the arrows 90. The reaction forces therefore do not form a couple which would tend to cause the piston 58 to rotate with respect to the drum, and in fact the entire drive means 56 rotates with the drum 20 as it causes rotation of the drum. This arrangement advantageously reduces wear on the piston seal 64 and also eliminates some of the friction forces caused thereby. Referring to FIG. 3, the arrows 92 and the arrow 94 indicate the direction of rotation of the members 80 and the drum 20, respectively, when winding the cable onto the drum.

It may be appreciated from the foregoing description-that the arrangement of the drive means 56 within the hollow interior 55 of the cable drum provides a substantial enclosure for protecting the mechanism from damage and contamination due to dirt and dust. The bearings and gearing may be suitably lubricated by an application of grease on assembly or a small quantity of oil may be provided in the interior 55 to splash over the elements therein as the drum rotates.

The operation of the balancing hoist is believed to be evident from the foregoing description of the structural features. The shaft 38 includes a longitudinal passage 96 in communication with conduit 34 and with the pressure chamber 60 through openings 98 for conducting pressure fluid such as compressed air to or from said chamber. Admission of pressure fluid to the chamber 60 to act on the piston 58 will cause the same to move toward the members 80 and drive the drum 20 rotatively as aforedescribed. Exhausting pressure fluid from the chamber 60 will result in the load pulling the cable unwinding same from the drum as it rotates in the opposite direction to that indicated by the arrow 94 and causes the cam gear members 80 to move the piston 58 toward the end plate 48. As also previously mentioned, a control system which will suitably operate the balancing hoist 10 to raise, lower, or balance a load is disclosed in US. Pat. No. 2,939,431. By connecting the conduit shown in the schematic views of the aforementioned patent drawing to the pressure chamber 60 instead of the referred to cylinders" suitable operation of the balancing hoist 10 may be obtained.

What is claimed is:

1. A fluid-operated hoist comprising:

a frame;

a cable drum rotatably mounted on said frame and adapted to wind a flexible cable or the like thereon, said cable drum including a portion having an inner wall defining a hollow interior;-

a piston movably disposed within said hollow interior of said cable drum and sealingly engaged with said inner wall to form a pressure chamber within said hollow interior;

conduit means in communication with said pressure chamber for supplying pressure fluid to said pressure chamber to move said piston with respect to said cable drum; and,

drive means interconnecting said cable drum and said piston responsive to the movement of said piston to rotate said drum with respect to said frame.

2. The invention set forth in claim 1 wherein:

said drive means is located substantially within said hollow interior of said cable drum and is supported by said cable drum.

3. The invention set forth in claim 1 wherein: said drive means including said piston is operable to rotate with said cable drum in response to operating to rotatably drive said cable drum.

4. The invention set forth in claim 1 wherein:

said piston is supported by said frame and is operable to move axially with respect to the rotational axis of said cable drum in response to the admission of pressure fluid to said pressure chamber.

5. The invention set forth in claim 1 wherein:

said drive means includes a gear means rotatably mounted on said cable drum and engaged with gear means stationary with respect to said frame.

6. The invention set forth in claim 5 wherein:

said drive means includes means operable to rotate said gear means on said cable drum in response to the movement ofsaid piston.

7. The invention set forth in claim 6 wherein:

said means operable to rotate said gear means includes cam means connected to said gear means and cam driver means connected to said piston.

8. The invention set forth in claim 7 wherein:

said frame includes shaft means supporting said cable drum rotatably thereon, said shaft including said stationary gear means, and said gear means on said cable drum include a plurality of gears spaced one from another around said shaft and forming a planetary gear drive. 

1. A fluid-operated hoist comprising: a frame; a cable drum rotatably mounted on said frame and adapted to wind a flexible cable or the like thereon, said cable drum including a portion having an inner wall defining a hollow interior; a piston movably disposed within said hollow interior of said cable drum and sealingly engaged with said inner wall to form a pressure chamber within said hollow interior; conduit means in communication with said pressure chamber for supplying pressure fluid to said pressure chamber to move said piston with respect to said cable drum; and, drive means interconnecting said cable drum and said piston responsive to the movement of said piston to rotate said drum with respect to said frame.
 2. The invention set forth in claim 1 wherein: said drive means is located substantially within said hollow interior of said cable drum and is supported by said cable drum.
 3. The invention set forth in claim 1 wherein: said drive means including said piston is operable to rotate with said cable drum in response to operating to rotatably drive said cable drum.
 4. The invention set forth in claim 1 wherein: said piston is supported by said frame and is operable to move axially with respect to the rotational axis of said cable drum in response to the admission of pressure fluid to said pressure chamber.
 5. The invention set forth in claim 1 wherein: said drive means includes a gear means rotatably mounted on said cable drum and engaged with gear means stationary with respect to said frame.
 6. The invention set forth in claim 5 wherein: said drive means includes means operable to rotate said gear means on said cable drum in response to the movement of said piston.
 7. The invention set forth in claim 6 wherein: said means operable to rotate said gear means includes cam means connected to said gear means and cam driver means connected to said piston.
 8. The invention set forth in claim 7 wherein: said frame includes shaft means supporting said cable drum rotatably thereon, said shaft including said stationary gear means, and said gear means on said cable drum include a plurality of gears spaced one from another around said shaft and forming a planetary gear drive. 